Tire Safety and Shelf Life
A common method that I see time and time again for determining how safe a tire is, is to do the penny test. If the tire passes this test then the owner assumes that the tire is safe. Not only is relying on this method wrong, it can be a fatal mistake. The truth is, it doesn’t matter what the tread depth is, if the tires are old, they are dangerous. This is true for tires even when they have never spent a day on the road. The rubber compounds in a tire deteriorate with time, regardless of the condition of the tread.
Many car manufacturers recommend that tires should be replaced every six years while tire manufacturers like Michelin and Continental suggest that a tire can last up to 10 years as long as they are inspected yearly.
You could think about an old tire almost like an old rubber band. If you try to stretch an old rubber band you will see cracks in the rubber. This is true regardless of whether the rubber band has been in use or not.
There are tires that are specifically designed for higher mileage and have antiozonant chemical compounds built into the rubber but just because they are designed this way, they will still succumb to age.
There are certain factors that can dramatically reduce the lifespan of a tire. These include:
- Heat – tires age quicker in warmer climates. Also environmental conditions such as exposure to sunlight and coastal climates, can hasten the aging process.
- Storage – tires that haven’t been used and are just sitting in a tire shop or your garage will age at a slower rate than one that has been put into service on a car. However, it will still age no matter what.
- Conditions of use – This refers to how the tire is treated. Is it properly inflated? Underinflation causes more tire wear. Has it hit the curb too many times? Has it ever been repaired? Tires on a car that’s only driven on the weekends will age differently from those on a car that’s driven daily.
I have seen statistics that claim X amount of crashes a year are caused because of old tires but there isn’t really any evidence to prove those theories.
How to Know the Age of a Tire
If you look at the sidewall of a tire, you will see plenty of letters and numbers that are all there for a reason. To know the age of a tire you only need to know the DOT number. This number allows you to know the place and date of a tire’s manufacture.
If the tire was made after the year 2000, it will have a four digit code. The first two numbers indicate the week of manufacture while the last two numbers indicate the year. As an example, if the DOT code of a tire is 1119, it means that the tire was made in the 11th week of 2019.
In this example, the tire was made in the 23rd week of 2010.
If the tire was made before the year 2000, it would have a three digit code. The first two numbers indicate the week as before whereas the third number indicates the year in the decade that the tire was created. This makes it harder to decipher as you would need to know what decade it was. Some of those tires made in the 1990s (but not all) have a triangle after the DOT code, denoting that decade. But for tires without that, a code of “328” could be from the 32nd week of 1988 — or 1978. The best, and smartest thing that you can do if you have a tire with a three digit code is to get it replaced immediately.
Even armed with the knowledge of how old a tire is, you shouldn’t rely on that information alone as to know whether the tire is safe. You should give it a regular visual inspection also to check for any tread distortion or large or small hairline cracks in the sidewall.
The majority of people who choose to drive on outdated tires do so to save themselves money (tires are not cheap). This is risky and dangerous not only for the driver of the vehicle but also other drivers on the road. Take the initiative and change vehicle tires every six years, or sooner, to avoid a potentially dangerous situation.